1. Field of the Invention
This invention relates to an improvement applicable to a wire guide for wire electrode type electrical discharge machining. More specifically, this invention relates to an improvement applicable to a wire guide for enabling the wire guide to be employed both for taper machining and for non-taper machining while realizing high machining accuracy, regardless of the magnitude of the taper angle thereof, for enabling the wire guide to be readily connected to (or threaded with) a wire electrode, and additionally for enabling the wire guide to be employed in a wire electrode type electrical discharge machining apparatus equipped with an automatic wire electrode connecting (or threading) system.
2. Description of the Related Art
Wire guides for wire electrode type electrical discharge machining available in the prior art are classified into several categories, which are described below.
a. V-groove guide
Referring now to FIG. 1, a first prior art guide type is a V-groove wire guide 1. The V-groove guide 1 has a V-shaped groove along which a wire electrode 2 is guided. Although such a wire guide 1 is readily connected to (or threaded with) a wire electrode 2, or a wire electrode 2 can be easily attached to this guide 1, this V-groove guide 1 is not suitable for taper machining.
b. Die guide
A die guide 3, as illustrated in FIG. 2, exemplifies a second type of prior art wire guides. The die guide 3 has an aperture 31 through which a wire electrode 2 passes. The die guide 3 is suitable for taper machining.
c. Three-point-supporting guide
Referring to FIG. 3, a third type of wire guide is illustrated. A three-point-supporting guide 4 is a combination of a V-groove guide member 41 and a supporting guide member 42. This three-point-supporting guide 4 supports a wire electrode 2 accurately at a required location during a machining operation. The three-point supporting guide 4 is readily connected to (or threaded with) a wire electrode 2 by moving the supporting guide member 42 apart from the V-groove guide member 41.
d. Arc-shaped guide
An arc-shaped guide 5 according to the prior art is illustrated in FIG. 4. The arc-shaped guide 5 is a type of die guide of which the radius of curvature of the surface of an aperture 51 is extremely large. A wire electrode 2 used in the arc-shaped guide 5 will not be sharply bent, even if the taper angle is large. This construction presents a large magnitude of friction from being applied to the wire electrode 2.
Each of the aforementioned prior art wire guides for wire electrode type electrical discharge machining has drawbacks, which are described below.
The V-groove guide 1 of FIG. 1, in addition to not being suitable for taper machining, has a further disadvantage wherein the wire electrode 2 is deformed, as shown by a chain line 21 rather than remaining straight. This results in deteriorating machining accuracy.
The radius of curvature of the die guide 3 of FIG. 2 is inclined to be selected somewhat small. In this case, the die guide 3 has a drawback wherein the wire electrode 2 will be sharply bent, which will result in lower precision cutting.
When the taper angle is large for the three-point-supporting guide 4 of FIG. 3, the wire electrode 2 is likely to be curled. This is because a large magnitude of taper angle causes the wire electrode 2 to be sharply bent. Once again, the resulting machining will not be highly accurate.
When the selected diameter of the aperture 51 of the arc-shaped guide 5 is small, the arc-shaped guide 5 does not have any particular drawback, insofar as the machining accuracy in taper machining is concerned. However, an arc-shaped guide 5 having a small aperture 51 cannot be used in a system employing an automatic wire connecting system (or an automatic threading system).